Shells

• Interface to communicate with kernel
  

• Unix Shells
  

• 常見Unix 指令: UNIX 常見指令教學

• Shell Environment Variables
  

• Variables and Strings Quotes
  
  

• Shell Special Characters
  

  • ex:
    

• Built-in Shell Commands

• Input/Output Redirection
  

• File and Directory Related Commands
  

• Select and File Processing Related Commands
  

  • Example usage:
    • Find the occurrence of certain pattern in file
      grep -l harry *
    • Print the line number when using grep
      grep -n harry /etc/passwd
    • print the processes owned by harry
      ps auxww | grep ^harry
    • List harry’s id, uid, home, shell in /etc/passwd
      grep harry /etc/passwd | cut -f1,3,6,7 -d:
      
    • Cut out file permission and file name from ls output
      ls -l | grep -v ^total | cut -c1-11 -c47-
      • -c1-12: 1 st ~12 th characters (start from 1, instead of 0)
      • -c47-:characters after 47 th character (include 47 th)
    • Use awk to generate the same behavior of cut
      awk -F: '{print $1 " " $6}' /etc/passwd
    • Sort
      
      ls -al | sort -k 5,5 -r
      
    • tr -Translate characters
      • Change all alphabet to uppercase
        tr "A-Z" "a-z" < file1 > file2
      • Change all character to another charater
        grep lctseng /etc/passwd | tr ":" "\n“
      • Delete tab in file1
        tr -d "\t" < file1
      • Delete multiple space in file1
        tr -s " " " " < file1

• xargs Command
  
  
  

  • want to ping all hosts in file
    

• Command History in (t)csh